A conventional pressing mechanism for paper cutting device is disclosed in FIGS. 1 and 2 and generally includes a frame 11 including a first board 112 with two second boards 111 connected to two ends of a front side of the first board 112. A U-shaped bracket 12 has two extensions on two ends thereof and a threaded rod 13 extends trough the two extensions and a wheel 14 is connected to a top end of the threaded rod 13. Two circular plates 114 are connected to two rods on the two second boards 111. Two toothed member 153 each have teeth 1531 defined in a curve side thereof and are respectively connected to two link assemblies 15. Each link assembly 15 includes a first piece 151 and a second piece 16, the first piece 15 has a hole 152 so as to pivotably mount to the two rods and the second piece 16 has a pin which is pivotably connected an end of a pressing member 17. Each toothed member 153 has a connection portion 1532 which has a groove 1533 in which the respective one of the two circular plates 114 is engaged. The pressing member 17 can be lowered or raised by rotating the wheel 14 and the two toothed members 153 are then pivotable about the two rods by the rotation of the threaded rod 13 to drive the teeth 1531 on the toothed members 153. The teeth 1531 are directly engaged with the threaded rod 13 and driven by the threaded rod 13 so that there is a serious wear-out problem for the teeth 1531 and the threaded rod 13.
The present invention intends to provide a pressing mechanism that has a simpler structure and is reliable for long-term of use.